OBJECTIVE AND IMPORTANCE: This case illustrates an unusual complication of neuroendoscopic third ventriculostomy. CLINICAL PRESENTATION: A 30-year-old man with established hydrocephalus was treated with neuroendoscopic third ventriculostomy during which bleeding occurred from a vessel deep in the floor of the third ventricle. He subsequently had a third nerve palsy and developed frontal lobe infarction. INTERVENTION: The complication was treated conservatively. The patient subsequently required shunting. CONCLUSION: The cause of the infarction is discussed. The general issue of complications of this procedure is explored with a call for more open reporting of such occurrences.